Flynn's Classification

FLYNN'S CLASSIFICATION

In 1966, Michael Flynn proposed a classification for computer architectures based on the number of instruction steams and data streams (Flynn’s Taxonomy).

·        Flynn uses the stream concept for describing a machine's structure.

·        A stream simply means a sequence of items (data or instructions).

·        The classification of computer architectures based on the number of instruction steams and data streams (Flynn’s Taxonomy).

Flynn’s Taxonomy

·        SISD: Single instruction single data

–  Classical von Neumann architecture

·        SIMD: Single instruction multiple data

·        MISD: Multiple instructions single data

–  Non existent, just listed for completeness

·        MIMD: Multiple instructions multiple data

–  Most common and general parallel machine

SISD

·        SISD (Singe-Instruction stream, Singe-Data stream)

·        SISD corresponds to the traditional mono-processor ( von Neumann computer). A single data stream is being processed by one instruction stream

·     A single-processor computer (uni-processor) in which a single stream of instructions is generated from the program.

SIMD

·        SIMD (Single-Instruction stream, Multiple-Data streams)

·        Each instruction is executed on a different set of data by different processors i.e multiple processing units of the same type process on multiple-data streams.

·        This group is dedicated to array processing machines.

·        Sometimes,  vector processors can also be seen as a part of this group.

MISD

·        MISD (Multiple-Instruction streams, Singe-Data stream)

·        Each processor executes a different sequence of instructions.

·        In case of MISD computers, multiple processing units operate on one single-data stream .

·        In practice, this kind of organization has never been used

MIMD

·        MIMD (Multiple-Instruction streams, Multiple-Data streams)

·        Each processor has a separate program.

·        An instruction stream is generated from each program.

·        Each instruction operates on different data.

·     This last machine type builds the group for the traditional multi-processors. Several processing units operate on multiple-data streams